The electronics industry is tasked with providing reliable circuitry, such as to satisfy the need for uninterrupted reliability for as long as 10 years or more. Corrosion-induced service failures are one source of reliability failures. For example, corrosion of printed circuit boards (PCBs) and IC die can have the effect of causing electrical opens, as well as electrical shorts when the corrosion products creep among the electrical conductors. This shorting mode, sometimes referred to as creep corrosion, is exacerbated when sensitive electronic products (having exposed corrodible metal) are deployed in regions of the world that have significant levels of air pollutants which may be corrosive to metals (e.g., Cl2, H2S, NH3, SO2, and NO2).
Bond pad and interconnect line corrosion can be mitigated in several ways. The electrically conductive materials used can be selected more wisely, such as based on available corrosion data. The electrically conductive materials can be protected from the pollutants by the use of protective coatings, device enclosures, or in some limited applications by the relocation of equipment to more protected environments. Humidity is a chief contributor to corrosion, as water allows intimate access of concentrated contaminating species (some of which become strong acids in the presence of water) and transportation of corrosion products. A passivation layer comprising silicon nitride or silicon oxynitride may provide better environmental performance as compared to conventional silicon oxide passivation, but the passivation layer needs to be exposed over the bond pad areas to allow electrical contact thereto, typically by a bondwire, which renders the exposed bond pad areas susceptible to corrosion.